After the first day of January, 1963, where any county is bounded by the middle of the channel of any stream or watercourse, any change of such channel, whether by accretion, reliction, or avulsion, shall not bring about a change in the taxable situs of the property, and for all county and state purposes the boundary line will remain as originally shown on the tax rolls. Provided, that, as to such property which may have become subject to litigation as a result of being carried on the tax rolls of two or more counties prior to the enactment of this section, or shall subsequently become subject to litigation as a result of being carried on the tax rolls of two or more counties without either being prior in point of time, such dispute shall be resolved by final decree of the court.